1. Field of the Invention
The present invention relates to the general field of nuclear medicine. More particularly, it relates to a medical unit utilized for withdrawal, calibration, dilution and/or injection of a radioactive substance intended for being injected to a patient.
2. Description of the Related Art
Some radioactive substances are particularly useful in the medical field, for example in imaging procedures, as contrast agents or as therapeutic agents.
In order to limit the doses of radiations received by the patient and by the personnel in charge of the manipulations, use is made of medical-use short half-life radioelements, namely radioactive products whose level of emitted radiation decreases rapidly with time.
But, with such short half-life radioactive products, it is problematic to administer a suitable dose to the patient. The corresponding dosage must be very precise; it must take into account the time necessary for preparing the dose to be injected as well as the possible time between the moment of preparation of the product dose and the moment of injection itself of this dose to the patient.
Further, despite the type of products implemented (short half-life), another constraint to be taken into account relates the radioprotection of the medical personnel in charge with the preparation of the radioactive dose and the injection of it to the patient. This radioprotection has also to be effective for the patient.
In a classical manner, the doses to be injected are withdrawn in a syringe provided with a suitable shielding and placed itself in a shielded enclosure equipped with suitable measuring and controlling means that enable the aimed dose of radioactive product to be withdrawn. Next, an operator picks up the shielded syringe and goes to the patient to make the injection.
However, this way of proceeding does not offer an optimal security, as far as both operator radioprotection and precision of the dose injected to the patient are concerned.
Document U.S. Pat. No. 6,767,319 describes an equipment for calibration and injection of a radioactive product, aiming to limit personnel exposure to the radioactive substance and also to optimize the patient security.
The corresponding installation comprises three separate radioprotective enclosures, each including:                means for supporting a source of injectable radioactive product,        means for supporting a syringe, that are equipped with means for automatic operation of the plunger of the latter and that are associated with a device of the activimeter type for measuring in real time the radioisotopic activity from the product contained in the syringe, and        a system of valves.        
This system of valves is hydraulically connected, through tubes, to the enclosure containing the radioactive mother source, to the enclosure containing the syringe, to a source of physiological saline solution and to an injection catheter intended for being connected to the patient.
This equipment further comprises means intended for driving the system of valves and the means for operating the syringe plunger, in such a way to ensure, in a first time, withdrawal of a dose of radioactive product and/or of physiological saline solution into the syringe, and in a second time, ejection of the withdrawn radioactive product and/or physiological saline solution through the injection catheter. The dose of radioactive product is measured by the activimeter device during withdrawal into the syringe.
In this equipment, the tubes that connect the enclosure containing the system of valves and those containing the syringe or the radioactive source are not protected and are sources of radioactive emissions into the environment. Moreover, because of the structure thereof, the corresponding equipment is cumbersome. Further, complexity of the network of tubes leads to the presence of significant dead volumes.